1. Field of the Invention
The present invention relates to a tape synchronizing apparatus for a tape reproducer and, more particularly, to an apparatus adapted for use in an editing system.
2. Description of the Prior Art
In a video tape editing operation, when a desired video image on a recorded original tape is to be inserted into a predetermined portion of an edit tape for example, time codes respectively representing the beginning of the desired video image on the original tape (edit point on the original tape side) and the begining of the predetermined portion of the edit tape (edit point on the edit tape side) are designated in an editing apparatus. Then the tapes loaded in the individual tape reproducers are rewound by predetermined amounts from the designated time codes, and reproduction is started at such position. In this stage of operation, a reference time counter is set at a value anterior to a certain target instant for a time corresponding to the rewind amount and serves to measure the reference time simultaneously with start of the tape transport motion.
While the time codes are detected from the individual tapes before arrival at the edit point, the difference between the detected time codes and the respective designated edit-point time codes is calculated, and then the motions of both the original tape and the edit tape are controlled (synchronized) in such a manner that each difference coincides with the remaining time of time of the reference time counter. And when the remaining time of the reference time counter has finally become zero to indicate arrival of each tape at the designated edit point, the video recorder with the edit tape is placed in a recording mode to record the signal reproduced from the original tape.
Similarly, when video images obtained from the original tape are used for broadcasting, time codes are designated with regard to a desired reproduction instant and the beginning of a desired video image on the original tape. Then the original tape is rewound by a predetermined amount and begins to be reproduced at an instant anterior to the desired reproduction instant for a predetermined time. And synchronization is performed in relation to the reference time counter so that proper reproduction can be started without any disorder at the desired reproduction instant.
In the initial stage of such synchronization, the reproduced time code of each tape is delayed from the reference time before the original tape or the edit tape completely rises to the normal steady or constant speed thereof from the halt state. For the purpose of canceling such delay, there is preset in the reference time counter a value further anterior to the value corresponding to the rewind amount of each tape.
The tape-speed rise time varies depending on the type of each video tape recorder/reproducer or on individual apparatus even when the type is the same, and also on the length of each cassette tape (diameter of each reel), tape positions (beginning, middle and end), ambient conditions, total operation time period and so forth.
Therefore it has been necessary to select the greatest value as the delay time due to the rise of the tape speed. Accordingly, at the instant the tape speed has risen to the normal steady or constant speed, there is generally induced that the time code difference up to the edit point on the tape has a deviation from the remaining time in the reference time counter. And consequently a sufficient tape rewind amount needs to be taken for phase modification to attain synchronism. If the tape rewind amount is not sufficient, there may occur a fault that complete phase modification fails to be achieved at the edit point.